Explosive device



July 5, 1960 D. 1.. CQURSEN 2,943,571

EXPLOSIVE DEVICE 5 Sheets-Sheet 1 Filed March 18, 1958 FIG.

ATTORNEY y 1960 D. L. COURSEN 2,943,571

EXPLQS'IVE DEVICE Filed March 18, 1958 5 sh ..s 2

FIG. 2C

INVENTOR DAVID LINN COURSEN 6%. wiy aw ATTORNEY July 5, 1960 D. L.COURSEN 2,943,571

EXPLOSIVE DEVICE Filed March 18. 1958 5 Sheets-Sheet 3 VENTOR DAVID LINNRSEN ATTORNEY July 5, 1-9 0 D. L. COURSEN 2,943,571

BXPLOSIVB DEVICE Filed March 18, 1958 5 Sheets-Sheet 4 [:1 [I] I: I: E]I: E! [:I DDUDDUDDDEIUEIEIEIDDU ET{IIEIEIEIUUEIUEIDEIDETEIEIEI INVENTORDAVID LINN COURSEN fizz;

ATTQRNEY July 5, 1960 Filed March 18, 1958 D. L. COURSEN 2,943,571

EXPLOSIVE DEVICE 5 Sheets-Sheet 5 INVENTOR DAVID LINN COURSEN BY %m2 MATTORNEY 2,943,571 EXPIJOSIV'E DEVICE David L. Coursen, Newark, Del.,assignor to I. du Pont de Nemours and Company, Wilmington, Del., acorporation of Delaware Filed Mar. 18, 1958, Ser. No. 722,329 6 Claims.01. 102-22 The present invention relates to a novel high-explosivedevice wherein the natural detonation front is distorted.

More particularly, the present invention relates to a high-- explosivedevice wherein a detonation front generated at one point is made toarrive simultaneously at a plurality of points along a desired line. v

When a mass of a high explosive is initiated at one point, the resultantdetonation wave proceeds outwardly from the point at uniform velocity inall directions. For example, when a thin, flat circular charge of a highex-' plosive is initiated at the center, the detonation front proceedsthrough the charge in'the form of an expanding circle and arrivessimultaneously at all points along the perimeter of the charge. When thethin, flat charge has straight line boundaries, the detonation frontinitially constitutes an expanding circle until the portion of theboundary nearest the point of initiation is reached, thereafter thefront travels through the remainder of the charge as an expanding arc ofa circle, the radius of curvature of the are at any given point in thecharge being determined by the distance from the initiation point. It issimultaneously at a number of points along a curved line which does notcoincide with the natural curvature of the detonation front. a In manyindustrial-applications of explosives aside from blasting, improvedresults are obtainable when the explosive charge is initiatedsimultaneously at a plurality of points along its surface.- For example,when a linear, or wedge-like, shaped charge, such as'that described inU.S. Patent 2,605,704 (Jacques Dumas, Aug'. 15, 11952), for slottingpipe and thezlike, is initiated 'at a plurality-of points in a straihtilinealong its surface, rather than at one point, increased uniformityof penetration is obtained. Also, in the method of joining metalelements explosively as'de'scribed in U.S. Patent 2,367,206 (C. 0.Davis, to du Pont, J an. 16, 1945),1ocalized initiation of the explosivecharge surrounding the metal sleeve in the assembly sometimes results indamage tothe juncture, whereas such damage'does not occur when thesleeve-like chargeis initiated at a "plurality of points around one endof the charge;

Q'I'he use of aseries of individual initiators, such as blasting caps,to effect the simultaneous initiation at a .num'ber of points along astraight or curved line is not always feasible, because theeccentricities of the individual initiators; although slight enough tobe generally ignored, precludethe" accomplishing of the desired trulysimultaneous initiation. Moreover, the'mechanical assembly of'a la'r'genumber' of the initiators adjacent to the surface ofthe high explosiveto be initiated is extremely diflicult,

if not impossible, du'e'to' space requirements. -The bri-' :1;

sance, or shattering action, of the individual initiator also P A v, I2,943,571

prohibits the use of such a large number of the initiators in closeproximity because of their destructive efiects. The provision of a linewave generator, Le. a device where in a detonation front is generated atone point is distorted so that it arrives simultaneously at a number ofpoints along a straight or curved line, is of great value in the art.

One type of such a line wave generator has been provided and comprises aflexible sheath containing a number of inert spacing members which forma network of interstices in which is disposed a high explosive. Thisdevice, which is described in U.S. Patent 2,774,306 (N. A. MacLeod, Dec.18, 1956), effects the requisite in-' itiation but sufiers from thecomplexity of design, .the'

number of components in the device resulting in complications offabrication. As is apparent, the provision of an' effective line wavegenerator of simplified design is highly desirable.

Accordingly, an object of the present invention is the provision of animproved device wherein the detonation front generated at a point sourceis made to arrive simul taneously at a plurality of points along acurved line or one or more straight lines. Another object of the presentinvention is the provision of a line wave generator characterized bysimplicity of design. A further object of the present invention is theprovision of an explosive device whereby the initiation of an adjacentexplosive charge at a plurality of points along its surface is inducedsimul-' taneously in an efficient manner. Other objects will becomeapparent as the invention is further described. I have found that theforegoing objects may be achieved when I provide as the line wavegenerator a continuous sheet-like matrix of a high explosive, the matrixbeing defined by a plurality of aperatures of dimensions suflicient toprevent the propagation of the detonation wave.

across the aperture, the apertures delimiting a series of paths from theinitiation point to each of a plurality of finish points, each of thepaths being of sufiicient crosssectional area to support the detonationwave, the shortest detonation path being equal for each initiationpointfinish point route.

In order to describe more fully the nature of the present invention,reference now is made to the accompanying drawings in which: i

Figure l isa visual consideration of the theory involved in the presentinvention,

Figures 2A-G represent various embodiments of the line wave generator ofthe present invention, which embodiments are constructed in accordancewith the principles illustrated in Figure 1.'

-Referring now to the figures in greater detail, Figure 1 represents ahypothetical case in which a sheet-like charge of a high-velocitydetonating composition, completely irregular in its shape, is providedwith numerous,

irregularly shaped apertures randomly disposed within the sheet. Theexplosive composition constitutes a continuous matrix. When the chargeis initiated at point P the starting point, the detonation proceedsoutwardly at a given velocity along various routes R, indicated by thedotted lines in the figure, between point P and the finishpoints, P P PP constituting line L along the periphery of the charge. The mines, R,taken by the detonation wave are delimited by the position and size ofthe' randomly spaced apertures, and, in'all cases, thev routes are alonga path of cross-sectional area, W equal to or greater than the minimumrequired to prevent the 'Patented July 5,1960

3 size area, as indicated by the dotted lines of the figure. The factalso must be considered that for every high explosive of givencross-sectional area a certain air gap exists over which the detonationwave cannot propagate.

As illustrated in Figure l, the detonation wave travelsalong variousroutes which are of 'sufficient cross-see tional area to support thedetonation, the wave crossing over those air gaps sufiiciently small inmagnitude andb'y-passing those air gaps of a size suifici'ent to preventthe propagation of the detonation. Thus, it can be readily seen that thedetonation wave can be forced to take a predetermined and desired path.When the air gaps, regardless of their shape, are of sufiicientdimension to control the diversion of the detonation wave and are sodisposed that the shortest path for any starting point-finish pointroute is equal in length to all other shortest'starting point-finishpoint routes, the detonation wave arrives simultaneously at all thefinish points,

regardless of the exact configuration of the paths taken by the wave.

In Figures 2A-G are described various configurations constructed inaccordance with the principles of Figure 1. In all the configurations,the apertures are of sufficient dimension to prevent the propagation ofthe detonation across them and they delimit paths of suflicientcross-sectional area to support the detonation.

Figure 2A illustrates an embodiment of the present invention wherein thedetonation front generated at point P travels down routes R and arrivessimultaneously along a series of points P -P in a straight line. Thesheetlike high explosive is triangular in form and is perforated with anumber of apertures such that the matrix of explosive thus definedcomprises a series of parallel elongated, diagonal strips bounded on allsides of the high explosive.

The embodiment shown in Figure 213 comprises an equilateral triangleprovided with a regular hexagonal array of circular apertures, theapertures being centered at points of intersection of a rectangularcoordinate grid. In this embodiment, the detonation front generated atpoint P travels routes R and arrives simultaneously at a plurality ofpoints also in a straight line, some of the finish points beingindicated by P P In Figure 20, the sheet-like high explosive is in theform of an ogival triangle provided with a distorted hexagonal array ofcircular apertures, the apertures being centered at points ofintersection of a polar coordinate grid. The detonation front travelingfrom point P along routes R arrives simultaneously at a plurality ofpoints in a straight line, some of which points are indicated by P P Thedevice of Figure 2D also is triangular in shape and also produces astraight-line wave front, the detonation front arriving simultaneouslyat points P -P which are located along a straight line. In this case,the triangular sheet of high explosive is perforated with rows of nestedchevron shaped apertures, the rows being so disposed as to form straightcolumns of the apertures.

In Figure 2B, the line wave generator comprises an approximatelysemicircular sheet of a high explosive provided with rows of aperturesso disposed that the detonation Wave generated at point P afterby-passing one aperture is immediately confronted with another aperturewhich must be by-passed, the shortest start point-finish point path foreach finish point (some of which areindicated by P P being equal toevery other shortest start point-finish point path, so that thedetonation front arrives simultaneously at the finish points whichconstitute a straight line.

Figure 2F illustrates a line wave generator wherein a detonation frontgenerated at one point is made to arrive simultaneously at a pluralityof points along a circle. 'In this embodiment, the matrix of highexplosive constitutes a ring defining a circular hole, the points alongthe inner edge of the ring being the finish points, some of which 4 arerepresented by P -P The apertures defining the matrix are positionedsuch that the detonation wave after being diverted around one apertureencounters and must by-pass another aperture, the shortest detonationpath being equal for each start point-finish point route.

In Figure 2G showing an embodiment wherein the detonation frontgenerated at one point arrives simultaneously at a number of pointsdelineating a rectangle, the outer edges of the high-explosive matrixform a polyhedron and the inner edges define a rectangle. apertureswithin the matrix are so located that the detonation front generated atpoint P must, after by-passing one aperture, by-pass another, so thatthe shortest detonation path from the start point to each of the finishpoints (generally indicated by P .P delineating the rectangle is equalfor each start point-finish point route.

The following example serves to illustrate a specific embodiment of thedevice of the present invention. However, it will be understood to beillustrative only and not as limiting the invention in any manner. Theexplosive composition used in the example was flexible and sheetlike andcomprised an /15 mixture of PETN and a binder consisting of 50% butylrubber and 50% of a thermoplastic terpene hydrocarbon resin (Piccolytecommercially available from the Pennsylvania Industrial ChemicalCorporation and composed essentially of polymers of 18-pinene). Theexplosive composition is described in detail in co-pending applicationSerial No. 666,22-1-(0. J. Breza and C. 0. Davis, filed June 17, 1957,and assigned to the present assignee).

Example A 4.3-mm.-thiok sheet of the explosive composition having anexplosive loading of 4 grams per square inch was made up into thetriangular form illustrated in Figure 2B. The circular apertures were 6mm. in diameter and were provided on 9.25-mm. centers in a regularhexagonal array. The sheet was initiated at the apex by means of astandard electric blasting cap, and the detonation front traveledthrough the sheet to give a straight line detonation front.

As has been illustrated, the desired distortion of the detonation frontmay be achieved readily in a number of ways without-excessivecomplicationsof fabrication. The only critical features required toachieve the distortion are: (1) that the high explosive must be in theform of a continuous matrix, (2) that the apertures must be ofsuflicient dimension to prevent the propagation of the detonation waveacross the aperture, (3) that the initiation point-finish point pathsmust be of suflicient crosss'ectio'nal area to support the detonation,and (4) the shortest detonation path must be equal for each of theinitiation point finish point routes. Upon the basis of theseconsiderations, many variations of the line wave generator, 'in additionto the afore-described variations, may be prepared to produce lineardetonation fronts of various geometric forms.

'The exact explosive composition used is not critical so long as theexplosive material detonates at high velocity and can be formed into thenecessary continuous sheetlike'matrix. The exemplified composition of acap-sensitive crystalline *high explosive, e.g. PETN, and elastomerresinbinder detonates at a velocity of 6000-7000 meters per second and isreadily formed into the desired sheet for conversion into the continuousmatrix. As disclosed in the aforementioned application, this compositiongenerally contains 92.5-77.5 of the high explosive, the bindercontaining 25-75% of the elastomer. Although this com positionconstitutes the preferred high-velocity explosive, the use of otherhigh-velocity sheet-like explosives, e.g. sheets of blasting gelatin, iscompletely within the scope of the present invention.

Therdimensions of the apertures naturally are dependent upon thespecific high-velocity detonating explosive constituting the matrix,since the air gap necessary to The prevent the propagation of thedetonation wave is a function of the explosive. For example, theapertures in the exemplified explosive composition must have a minimumminor dimension of 0.020 inch, in order to provide the requisite airgap. Of course, this value will be different when other explosives, suchas blasting gelatin, are used, and, hence, the exact minor dimension ofthe aperture is not a fixed value.

Similarly, the minimum cross-sectional area required to support thedetonation is a function of the specific explosive forming the matrix.For the exemplified explosive material, this minimum area is 7.8 squaremillimeters. Since the cross-sectional area is dependent upon the widthof the web and the thickness of the explosive sheet, the minimumquantity of explosive required to support the detonation may also beexpressed by the relationship:

T W K wherein: T is the sheet thickness, W is the dimension (Width orWeb) for support of detonation, and K is a constant; For the exemplifiedexplosive composition, K is 0.72 mmf However, as stated previously inregard to the aperture size, the specific value for the cross-sectionalarea, and also for constant K of the thickness-width equation it use ofthe latter is desirable, will vary with the specific explosive used, theexact cross-sectiona1 area or constant not being a fixed value.

In many instances, for a given configuration of the line wave generatora mathematical expression correlating the required dimensions of thepaths with the air gap, or aperture size, may be formulated. As anexample, for this configuration of 243, i.e. a triangular sheet ofexplosive provided with a regular hexagonal array of circular holes, aperfectly straight detonation front is produced when:

W being the width of web of explosive between adjacent holes, W beingthe minimum width of web which will support a detonation, and R beingaperture radius. However, sufliciently straight fronts for many purposescan be obtained when the following equation is satisfied:

from the scope of the invention. For example, a number of the line Wavegenerators may be assembled, e. g. stacked, to give a plane Wavedetonation front, and the specific explosive used and the configurationand dimensions of the line wave generator may be varied. I intend, therefore, to be limited only by the following claims.

I claim:

1. A line wave generator wherein the natural detonation front generatedat one initiation point is distorted to arrive simultaneously at aplurality of finish points along a straight line which consists of acontinuous sheet-like matrix of a high-velocity detonating explosive,said matrix being defined by a plurality of apertures of dimensionssufiicient to prevent the propagation of the detonation wave across theaperture, said apertures delimiting a series of paths from the saidinitiation point to each of a plurality of said finish pointsdelineating said straight line, all of said paths being of sufficientcross-sectional area to support the detonation wave, the shortest suchpath from said initiation point to all of said finish points beingequal.

2. A line Wave generator according to claim 1, wherein said matrixconsists of a triangular sheet comprising a series of parallel,elongated diagonal strips bounded on all sides by said high-velocitydetonating explosive. 3. A line wave generator according to claim 1,wherein said matrix consists of a triangular sheet provided with aregular hexagonal array of circular apertures, said apertures beingcentered at points of intersection of a rectangur lar coordinate grid.

4. A line Wave generator according to claim 1, wherein said matrixconsists of an ogival triangular sheet provided with a distortedhexagonal array of circular apertures, said apertures being centered atpoints of intersection of a polar coordinate grid.

5. A line wave generator according to claim 1, wherein said matrixconsists of a triangular sheet provided with rows of nestedchrevon-shaped apertures, said rows being so disposed as to formstraight columns of the apertures.

6. A line wave generator according to claim 1, wherein said matrixconsists of a semicircular sheet provided with rows of apertures sodisposed that the detonation wave after by-passing one apertureencounters and must bypass another aperture.

References Cited in the file of this patent UNITED STATES PATENTSMacLeod Dec. 18, 1956

